Process of producing paper



mune 28, 1932. DB. OBLINGER PROCESS OF aonucme PAPER [Filed 001;. 29. 1929 ATTORNEYS Patented June 28, 1932 i at UNITE STATES PATENT OFFICE 13m 3. OBLINGER, OF NEW HOPE, PENNSYLVANIA. ASSIGNOR T0 UNION HILLS PAPER MANUFACTURING COMPANY, OF NEW HOPE, PENNSYLVANIA, A. COBPOBA- I TION OF PENNSYLVANIA PROCESS; Q1 PRODUCING PAPER Application filed October 29, 1929. Serial No. 403,145.

This invention relates to a process whereby paper of a particular finish can he produced under such conditions that the density of the finished product can always be controlled right from the initial steps. The process is particularly intended for the production of insulating paper such as is used in covering of hi h tension cables where both the finish and diansity are of rimary importance.

Heretofore in or er to give the paper the desired-finish it has been customary to subunit it to what is known as a supercalendering operation. In that process a fully dried web of paper is first passed through a moistoning machine where it is subjected to a spray or mist of waterand then ordinarily is rolled up and allowed to wait a few minutes so "that the moisture can properly temper the whole body of the paper. After the web is thus moistened, the paper is passed through a calender in which alternate rolls are faced with metal and with com ressed aper and the metal faced rollers are eated. The rubbing action which results from this treatment glves a somewhat different effect from that where all of the rolls are of metal and its use has heretofore been considered necessary to give the desired finish for insulating paper of the type referred to.

it is to be noted that the supercalendering operation demands at least two distinct operations with the paper wound up between them. This is not only expensive, but also renders it very dilficult to keep a constant check on'the density ofthe finished product. There are many variable factors entering into the question of density which must be watched through the production of the paper all the way from thev screen to the end of the drier; where'the operation is broken it is dificult to keep these variables under exact control and a slight change in any one of several factors may cause a resulting change in density sufiicient to injure the value of the product for electrical purposes.

By the process which is the subject of this application, the web is moved ontinuously,

from the screen through and out of the final .calender, with the result that there is only a brief time between the formation of the the bottom "roll of the first stack.

trolled the sheet will not be weakened to the breaking point and the water can be entirely dried out in the subsequent calenderin operation, and at the same time the desire fin ish can'readily be given to the paper.

In carrying out the invention, the paper passes continuously from the screen to the drier and thence to the calender stack. Here it is passed through several nips to harden its surface somewhat and then the water is applied to both faces of the sheet. This aplication of water is preferably accomplished y forming films of water on the face of two calender rolls which in turn carry the Water to the paper. By applying the water to the calender rolls in the form of a film the thickness of the film and thus the amount of water transmitted to the paper can be controlled with considerable accuracy. In this operation the moisture content of thepaper should be brought up to the figure in the order of from 15 to 25% of moisture, 20% being a' good working percentage to aim at. The

paper that has thus had its shrface layers well moistened continues through several additional nips which equalizes the moisture content over the surface. This moistening referably Y and preliminary calendaring is done in one calender stack and the al finishing is preferably conducted in an adjoining stack to which the paper passes directl from n the second stack the rolls are heated sufliciently to have a material drying action on the paper. Thus all of the rolls except the top and bottom roll can be heated with exhaust steam at a temperature of a few degrees above the boiling point. All of the rolls in this stack, like the first stack, are preferably metal faced. The action of the heated rolls on the wet surface of the paper gives it the desired finish and atthe same time dries out the sheet. I believe that this result is due to the fact that the surface layers. are wet to a somewhat greater degree than in the supercalendering operation but there is not sufficient time allowed forthe water to thoroughly permeate so that the sheet is uniformly wet, due to the fact that .the sheet moves directly from the moistening operation to the heated rolls where drying starts. An even more important result of the continuous operation right from the formation of the paper until its final finishing, is the control of density. If at any time the density of the finished stock is found to show a variation from the desired point, the operator can recognize this before such variation becomes serious and immediately can vary some of the preliminary steps in the production of the paper in such a way as to overcome the difiiculty. If desired, the paper may be semi-calendered while in the drier as is well understood in the art. This will not materially modify the subsequent procedure.

For the purposes of illustration I show in the a-ccompanyingdrawing the essential portions of the paper making machine used for carrying out my process, with the preliminary elements simply indicated as they form no part of the present invention except that they are directly connected with the finishing elements. In this drawing, Fig. 1 is a diagrammatic side view showing the course of manufacture, and Fig. 2 is a sectional view of two of the rolls on the first calender stack and the mechanism for forming controlled water films on these rolls.

In the drawing the numeral 10 indicates numbered from 1 to 8 inclusive beginning at the bottom. After the paper has passed between rolls 7 and 8 and 6 and 7 it approaches the nip between rolls 5 and 6 where one face is moistened, and the other face is moistened at the nip between the rolls 4 and 5. To supply the water for this moistening the rolls 4 and 5 are provided with moistening devices as shown in detail inFig. 2. It is to be understood that these are similar except for their reversal of position and that they, ex-

tenil for substantially the full length of the rol Each of the moistening devices comprises a support 28 carrying a metal trough 30 which has no metal side toward the roll. In

place of such metal side toward the roll, a

of heavy felt 36 which extends up above the leather member 32 and contacts wlth the face of the roll. Each trough may be kept full of water in any desired way as by a pipe 38. The wet felt 36 will cover the face of the roll with a film of water, and in order to control the thickness of this film a felt roller 40 is carried by each trough 32 and is tensioned toward the main roll on the calender by spring 42, the tension of which may be varied as bya thumb nut 44. The roll 40 will act as a squeegee to cause excess water to run back into the trough 30 and permit only the desired amount of water to continue to remain on the face of the roll and ultimately come in contact with the paper.

After the paper has been moistened on rolls 4 and 5 it continues down to the bottom of the stack and then is brought up to the top of an adjoining stack where all of the rolls are metal faced and where all except the top and bottom rolls are steam heated as by the steam connections 46 which lead from a steam pipe 48. In passing through the second calender stack the sheet is dried and given the desired finish so that it can go direct to a winder forshipment. The paper can be watched as it emerges from the second calender stack, and if it is found that there is a change in density a proper adjustment can be made in the paper forming machine or in the drier so as to immediately correct the difiiculty. The finish can also be varied by the amount of water transmitted to the paper from the troughs 32, as well as by the other factors known in the art.

It is to be understood that the equipment described is shown primarily for illustrating one way in which my process may be carried out, and that other forms of equipment may paper which.

the paper is partly calendered to compact the surface, then directly applying a film of water by means which allow a fine adjust ment, the web being run at such speed and the paper being wet to such a degree'that thorough permeation of the web does not take place and then runmng the paper through calender rolls heated to substantially 212 F.

2. The process oftreating aper which comprises the steps of assing t e paper between adjacent calen. er rolls ad usted to compact the surface, sup lying sufiic1ent amounts of water in the orm of films to the faces of such rolls to wet both surfaces of the paper without saturating the paper and thereafter passing such paper without interruption of movement throu h a series of calender rolls heated to su stantially 212 F.

3. A process as specified in claim 2 wherein the amount of water added to the pa r brings its moisture content by weight to tween 15% and 25%.

4. An apparatus for finishin paper, comprising a series of calender r0 s, a pair of water troughs positioned alongside of adjacent rolls but on opposite sides thereof, absorbent means for conducting water from such troughs to the faces of such rolls and separate adjustable means for -limiting the amount of water that is permitt d to remain on such rolls.

5. A structure as specified in claim 4, in which means is provided for pressing said troughs towards said rolls and said troughs are made with the side towards said rolls formed of leather so that the rolls will not be scratched.

6. The process of forming insulating paper comprising the steps of forming a web of paper, partly calendering such paper so its surface is compacted, applying water to the partly calendered aper, and then before the paper becomes t oroughly permeated by such water, subjecting the same to heated calenders which finish and dry the same, the paper in all the said steps being continuously conducted from one operation to the next without a break.

7. The process as specified in claim 6, whereinthe amount of water a plied to the paper brings the percentage 0? water contained therein up to between 15% and 25%.

8. The process as specified in, claim 6,.

wherein the heated calenders are heated to approximately 212 F.

DANIEL B. OBLINGER. 

